Halley's [HAL-lee] Comet has been know since at least 240 BC and possibly
since 1059 BC. Its most famous appearance was in 1066 AD when it was
seen right before the Battle of Hastings. It was named after
Edmund Halley, who calculated its orbit.
He determined that the comets seen in 1531 and 1607 were the same object
that followed a 76-year orbit. Unfortunately, Halley died in 1742, never
living to see his prediction come true when the comet returned on
Christmas Eve 1758.

Halley's Comet put on bright shows in 1835 and in 1910. Then in 1984 and
1985, five spacecraft from the USSR,
Japan and Europe were launched to make a rendezvous with Halley's Comet
in 1986. One of NASA's deep space satellites was redirected to monitor
the solar wind upstream from Halley. Only three comets have ever been
studied by spacecraft. Comet Giacobini-Zinner was studied in 1985, Comet
Halley in 1986, and CometGrigg-Skjellerup on July 10th, 1992. The nucleus
of Halley is ellipsoidal in shape and measures approximately 16 by 8 by 8
kilometers (10 by 5 by 5 miles).

Comet Halley in False Color
This image of Halley's Comets was taken during its 1986 appearance.
False-color digital enhancement was used to permit measurement of slight
brightness differences.
(Copyright Calvin J. Hamilton)

Giotto Mosaic of Halley's Comet
This image is a mosaic of 8 images taken by the Giotto spacecraft during the
Halley encounter on March 13, 1986. The nucleus dimensions are about 16 by 8 by 8
kilometers. By examining the dust jets being emitted from the nucleus, scientists
were able to determine that only about 10% of the surface was active.
(Courtesy A. Tayfun Oner)

Ion Tail
The well developed tail structure of Comet Halley was captured in this
image taken March 5, 1986. At this point in its orbit, Halley had
recently passed perihelion on February 9, 1986 and was at its most
active. This 10 minute exposure was recorded at Mauna Kea Observatory
on IIIa-J emulsion without filters. This image shows both the ion and
dust tail, with the latter stretching for over 6 degrees on the sky.
(Courtesy NASA/JPL)

Detachment Event
One of the more spectacular changes recorded for Halley during an
apparition was the detachment event that occurred on April 12, 1986.
This 3 minute exposure was taken using the Michigan Schmidt telescope
at Cerro Tololo Interamerican Observatory. The resulting image clearly
shows part of the ion tail structure detached from the comet. At this
period, the orientation of the comet is such that the tail is
foreshortened, with the prolonged radius vector pointing west of north.
(Courtesy NASA/JPL)

Ray Structure
An example of the ray structure of Halley was captured on March 19, 1986,
at the Mount Wilson/Las Campanas Observatories. This 10 minute exposure
was recorded at the focus of the 100 inch telescope on Las Camapanas in
Chile. The close up image, covering the inner 1 degree of the comet,
shows a prolonged radius vector extending to the left.
(Courtesy NASA/JPL)

Cylindrical Map of the Nucleus of Comet Halley
This image is a shaded relief map of the nucleus of Comet 1/P Halley.
It is the same map as the above image, but
reprojected to the Simple Cylindrical projection.
As with all maps, it is the cartographer's interpretation and
not all features are necessarily certain given the limited data
available. This interpretation stretches the data as far as is feasible.
Halley is a particularly difficult object to map, given the nature of the
data available. Many other interpretations might be possible. This
relief drawing represents an attempt to show features visible on the
disk in various spacecraft images, and the various ridges and hollows
suggested by limb topography.
(Courtesy Phil Stooke)

Map of the Nucleus of Comet Halley
This image is a shaded relief map of the nucleus of Comet 1/P Halley.
As with all maps, it is the cartographer's interpretation and
not all features are necessarily certain given the limited data
available. This interpretation stretches the data as far as is feasible.
Halley is a particularly difficult object to map, given the nature of the
data available. Many other interpretations might be possible. This
relief drawing represents an attempt to show features visible on the
disk in various spacecraft images, and the various ridges and hollows
suggested by limb topography.
(Courtesy Phil Stooke)